The invention relates generally to positioning devices. More specifically, it relates to an electromagnetic positioning device capable of providing a relatively precise mechanical output. Electromagnetic devices have been used for some time to function as linear or rotatable force motors in order to drive or position output shafts. For example, U.S. Pat. No. 3,883,839, assigned to the present assignee, disclosed an electromagnetic positioning device of a type similar to the present invention.
It is frequently desirable to move valves or other types of switches in a system through which fluid is flowing and to move valves to precise positions in order to accurately control the quantity of fluid flow flowing in the system as, for example, a throttle on a fuel delivery system for an engine. Frequently the valve is moved to a desired position by a rotatable element, such as a shaft, which may be actuated by hand or by a force motor either of the linear or rotary type.
Prior force motors have not always been sufficiently accurate nor have they been available to handle a wide variety of applications. Often it is necessary to construct a force motor designed for a given application in order that the precision for a desired application can be achieved.
Accordingly, it is an object of the present invention to provide a novel electromagnetic actuating device capable of moving a control element, such as a valve, to a precise position.
A further object of the invention is to provide such a device which is capable of achieving precise positioning over a wide range of force and displacement applications by cascading two or more force motors in series, as necessary.
Another object of the present invention is to provide a modular actuating device which is easily serviced and which can be assembled with as many force motor units as necessary for a given application.
A further object of the invention is to provide an actuator device which is low in cost and is of increased versatility.
Other objects and advantages of the invention will become apparent from the remaining portions of the specification.